Endovascular treatment of intracranial aneurysms: comparative evaluation in a terminal bifurcation aneurysm model in dogs

Object. The authors investigated whether HydroCoils decreased coil compaction and aneurysm recanalization in a canine model of a large, wide-necked, high-flow bifurcation aneurysm. Methods. Eleven experimental aneurysms were created. Two aneurysms were untreated (Group 1); three were treated with standard platinum coils (Guglielmi Detachable Coils; Group 2); and six were treated with platinum framing coils and filling HydroCoils (Group 3). Comparative angiographic and histopathological data were analyzed at 2 weeks and again at 3 months. At 3 months, the Group 1 aneurysms remained patent without spontaneous thrombosis. After coil placement the percentage of aneurysm filling by volume ranged from 59 to 90% (mean 75.4%) for Group 3 (HydroCoil-treated) and 34.3 to 48.9% (mean 39.6%) for Group 2 (GDC-treated) (p < 0.05). At 14 days, two of the three Group 2 aneurysms exhibited coil compaction and aneurysm recanalization at the neck; in both cases the condition worsened at 3 months. At 14 days and 3 months, five of the six Group 3 aneurysms were 100%, and one of six was 90% occluded and remained stable. At 3 months, the neointima of the aneurysm neck was significantly thicker in the Group 3 lesions, which had been treated by HydroCoils (0.329 +/- 0.191 mm), than in Group 2 lesions, which had been treated with GDCs (0.026 +/- 0.018 mm) (p < 0.001). No thrombus formation occurred in Group 2; however, in two of the six aneurysms in Group 3, thrombus formed at the coil-neck interface. Conclusions. The experimental canine bifurcation aneurysm model overcomes the limitations of side-wall aneurysm models. In this model, HydroCoils resulted in significantly denser coil packing, less follow-up coil compaction, and thicker neointimal tissue at the neck of the lesion. HydroCoils also appeared more thrombogenic at the aneurysm neck-parent artery interface.